Why pollsters are finding it hard to predict France's snap elections

France's two-round voting system means that "the parliamentary election is usually difficult to begin with," said an employee of one major survey firm.

But with new alliances and divisions within parties themselves, "we have no frame of reference now, the deck has been reshuffled," she added, asking not to be named.

Some pollsters have had to reimburse staff for cancelled or delayed holidays to cope with the extra workload, the person said.

In the French electoral system, voters in the country's 577 constituencies have a broad choice of candidates in the first round, which is set this time around for June 30th.

The two highest scorers plus any others who win backing from more than 12.5 percent of registered voters then proceed to the second round on July 7th.

If any candidate wins more than 50 percent in the first round then they win the seat without the need for a second round - this is rare in parliamentary elections but it does happen in some areas.

Voters often shift their support between the rounds, often at the behest of preferred candidates who fall short.

That makes prediction far more complex than the one-round proportional representation system in the June 9th European Parliament poll, when pollsters' forecasts were all close to the final score.

"We're losing a bit of sleep" ahead of the national ballot, said Jean-Daniel Levy, deputy director at Harris Interactive.

"The parliamentary election is the trickiest to grasp... it's 577 polls and their local foibles," he added.

Most opinion surveys are carried out online, with pollsters taking representative samples of over 1,000 people and asking where they live in a bid to smooth out constituency oddities -- allowing them to extrapolate to the national level.

On the face of it, voters have a choice between three headline blocs: Macron's centrists, the far-right Rassemblement National (RN) and the Nouveau Front Populaire (NFP) left-wing alliance.

An Ifop poll published Monday found that around 33 percent of people would vote RN in the first round, with the left at 28 percent and 18 percent for Macron's bloc.

In fact, "it's a lot more complicated," said Mathieu Gallard, research director at Ipsos, pointing for example to the "totally chaotic" situation within the right-wing Les Républicains party (LR).

The LR has imploded, with party chief Eric Ciotti calling for an alliance with the far right while other figures want to maintain their independence or align with Macron.

Such dynamics mean national-level forecasts of votes and seats come with a clear buyer-beware warning.

It is almost impossible to predict this time how voters might behave between the two rounds.

"Mistakes are all but certain and we don't know in which direction," said Jerome Sainte-Marie, a former pollster standing for the RN in eastern France.

"The 2022 election showed us that seat projections before the first round are extremely shaky," agreed Gallard. "It's only after the first round that we'll start to have a developing idea of the forces at play."

Two years ago, surveys overestimated backing for Macron's camp and underestimated the RN vote.

The party of Marine Le Pen was predicted to win 15 to 35 seats ahead of the first round, then up to 50 ahead of the second.

In the end, they brought in their largest-ever delegation of 89 MPs, overcoming a longstanding struggle for the far right to translate support into seats.

This year, "we're in a totally unprecedented period, it's almost impossible to understand what the political landscape will be in a week and a half," said Hugo Touzet, a sociologist specialising in polls.

"If we do things seriously, the margin of error is plus or minus 80 MPs for each bloc, it's huge," he added.

Harris's Levy told AFP that voters could return a "possible absolute or relative majority for the RN... repeating their voting behaviour at the European Parliament election".

He sees "a little momentum" for the left that is still "far short of triggering a swing in parliament".

On Macron's side, there's a "burst of mobilisation" that could prevent a re-run of their European rout.

Predictions made after the first-round results at 8pm on June 30th "could quickly go out of date" as voters update their preference before the second round on July 7th.

It could be that having "sent a message, voters don't want all the power in the hands of the RN", Levy said.

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